Linear compressor

ABSTRACT

Provided is a linear compressor including a linear motor having a mover reciprocating with respect to a stator; a piston coupled to the mover to reciprocate; a cylinder into which the piston is slidingly inserted, the cylinder having an inner circumferential surface forming a bearing surface together with an external circumferential surface of the piston, the cylinder forming a compression space together with the piston, and the cylinder having at least one first hole formed through the inner circumferential surface of the cylinder and an outer circumferential surface of the cylinder to guide refrigerant discharged from the compression space to the bearing surface; and a porous member inserted into the outer circumferential surface of the cylinder and configured to cover the first hole, the porous member having multiple micropores smaller than the first hole.

CROSS-REFERENCE TO RELATED APPLICATION

Pursuant to 35 U.S.C. § 119(a), this application claims the benefit ofearlier filing date and right of priority to Korean Application No.10-2018-0056138, filed on May 16, 2018, the contents of which isincorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a linear compressor capable oflubricating a space between a cylinder and a piston with refrigerant.

2. Background of the Invention

As reciprocating compressors, a crank-type reciprocating compressorcapable of compressing refrigerant by converting a rotational force of arotary motor into a linear motion and a vibration-type reciprocatingcompressor capable of compressing refrigerant by using a linear motorperforming a linear reciprocating motion are well known. Avibration-type reciprocating compressor is called a linear compressor,and such a linear compressor has no mechanical loss caused by conversionof a rotational motion into a linear reciprocating motion, therebyimproving efficiency and simplifying a structure.

Meanwhile, a linear compressor may be classified into an oil-lubricatedlinear compressor and a gas-lubricated linear compressor according to alubrication scheme. An oil-lubricated linear compressor has a certainamount of oil stored in a casing and is configured to lubricate a spacebetween a cylinder and a piston by using the oil, as disclosed in patentdocument 1 (Korean Patent Publication NO. KR10-2015-0040027). On theother hand, a gas-lubricated linear compressor has no oil stored in acasing and is configured to lubricate a space between a cylinder and apiston by guiding a portion of refrigerant discharged from a compressionspace to a bearing surface between the cylinder and the piston tosupport the piston with a gaseous force of the refrigerant.

An oil-lubricated linear compressor (hereinafter referred to as anoil-lubricated compressor) may restrain a cylinder and a piston frombeing overheated due to motor heat, compression heat, or the likebecause oil with a relatively low temperature is supplied to a bearingsurface between the cylinder and the piston. Thus, an oil-lubricatedcompressor may restrain refrigerant passing through a suction flow pathof a piston from increasing from being suctioned into a compressionchamber and heated, and thus it is possible to suppress an increase inspecific volume and thus to prevent occurrence of a suction loss.

However, an oil-lubricated compressor may experience that oil isinsufficient in a casing of the compressor when oil discharged to arefrigerating cycle apparatus along with refrigerant is not smoothlywithdrawn to the compressor, and the oil shortage in the casing maycause the reliability of the compressor to be reduced.

On the other hand, compared to an oil-lubricated compressor, agas-lubricated linear compressor (hereinafter referred to as agas-lubricated compressor) may be downsized, and has no reduction inreliability due to oil shortage because a bearing surface between acylinder and a piston is lubricated with refrigerant.

In such a gas-lubricated compressor, a loss of compressed refrigerantmay occur because a small amount of refrigerant is injected into abearing surface between a cylinder and a piston to support the piston bya gaseous force of the refrigerant. That is, the refrigerant flowing tothe bearing surface between the bearing surface between the cylinder andpiston leaks into an inner space of a casing due to a difference inpressure. Thus, the consumption flow rate of the compressed refrigerantincreases, and the loss occurs. Accordingly, in order to reduce theconsumption flow rate of the refrigerant, it is possible to consider amethod of decreasing the diameter of a nozzle part of a gas bearing ordecreasing the number of nozzle parts.

However, a conventional gas-lubricated compressor has an increasedmanufacturing cost for a cylinder because, as described above, aplurality of nozzle parts are finely formed in a cylinder but thisrequires a complicated post-operation as well as a considerabledifficulty in forming the fine nozzle parts.

Also, a conventional gas-lubricated compressor may have reducedreliability because, when the inner diameter of a nozzle part is madevery small or the number of nozzle parts is reduced in consideration ofthe consumption flow rate of the refrigerant, the possibility that thenozzle part is clogged by foreign substances increases.

Also, a conventional gas-lubricated compressor may have a decreasedload-bearing capacity for a piston because a pressure loss ofrefrigerant passing through a nozzle part may occur when the innerdiameter of the nozzle part is made small. As a result, fractional lossor abrasion may occur between a cylinder and a piston.

Also, a conventional gas-lubricated compressor has nozzle parts formedlengthwise of the cylinder in a plurality of rows, but a refrigerantpassage for guiding refrigerant to the nozzle parts may be biased tosome of the nozzle parts in the plurality of rows. Thus, morerefrigerant flows into the nozzle parts close to the refrigerant passagesuch that the load-bearing capacity for the piston may be non-uniformlyformed lengthwise.

Also, when a refrigerant passage for guiding refrigerant to nozzle partsis biased some of the nozzle parts in a plurality of rows, as describedabove, a conventional gas-lubricated compressor may have an increasedsuction loss because the refrigerant excessively flows into acompression space or may have an increased compression loss because therefrigerant leaks into an inner space of a casing. That is, when therefrigerant passage is formed close to a nozzle part adjacent to thecompression space, the refrigerant passing through the nozzle part flowsinto the compression space, thus increasing the suction loss. On theother hand, when the refrigerant passage is formed close to a nozzlepart farther from the compression space, the amount of refrigerantleaking into the inner space of the casing may increase, thus increasingthe compression loss.

Also, a conventional gas-lubricated compressor may have an increasedpressure loss because the space between a frame and a cylinder is nottightly sealed such that refrigerant leaks into an inner space of acasing before flowing into a nozzle part.

Also, a conventional gas-lubricated compressor has a filter installedoutside a gas bearing and at a suction side or a discharge side withrespect to the gas bearing to filter out foreign substances because theforeign substances flow to the gas bearing together with refrigerant.However, as a result, the number of components of the compressor isincreased, which causes an increase in manufacturing cost.

RELATED ART DOCUMENT Patent Document

(Patent Document 1) Korean Patent Publication NO. KR10-2015-0040027A(published on Apr. 14, 2015)

(Patent Document 2) Korean Patent Publication NO. KR10-2016-0024217A(published on Mar. 4, 2016)

SUMMARY OF THE INVENTION

Therefore, an aspect of the detailed description is to provide a linearcompressor capable of smoothly supplying refrigerant to a bearingsurface between a cylinder and a piston without a fine nozzle partformed in the cylinder.

Also, the present invention provides a linear compressor capable ofpreventing a flow path for guiding refrigerant to a bearing surface frombeing clogged by foreign substances and also restraining the refrigerantfrom excessively flowing to the bearing surface, thereby reducing aconsumption flow rate of the refrigerant.

Also, the present invention provides a linear compressor capable ofpreventing refrigerant flowing to a bearing surface from beingexcessively decompressed to secure an appropriate load-bearing capacityfor a piston.

Also, the present invention provides a linear compressor capable ofallowing refrigerant flowing to the bearing surface to secure a uniformload-bearing capacity lengthwise with respect to a piston.

Also, the present invention provides a linear compressor capable ofrestraining refrigerant flowing to a bearing surface from flowing into acompression space or from leaking into an inner space of a casing,thereby reducing a suction loss or a compression loss.

Also, the present invention provides a linear compressor capable ofrestraining refrigerant from leaking into an inner space of a casingbefore flowing to a bearing surface, thereby reducing a compressionloss.

Also, the present invention provides a linear compressor capable ofsuppressing an increase in outer diameter even though a separate filtermember is provided between a frame and a cylinder.

Also, the present invention provides a linear compressor capable ofeliminating a filter for restraining foreign substances from flowing toa bearing surface along with refrigerant to decrease the number ofcomponents, thereby simplifying a structure and also reducing amanufacturing cost.

To achieve these and other advantages and in accordance with the purposeof this specification, as embodied and broadly described herein, thereis provided a linear compressor for supplying compressed refrigerant toa bearing surface between a cylinder and a piston and supporting thepiston against the cylinder by a gaseous force of the refrigerant, thelinear compressor including a porous member having micropores in themiddle of a refrigerant passage through which the compressed refrigerantis supplied to the bearing surface between the cylinder and the piston,wherein gas holes larger than the micropores are formed inside andoutside the porous member.

Here, the gas hole inside the porous member and the gas hole outside theporous member may be formed at radially different locations.

Also, the gas holes inside the porous member and the gas hole outsidethe porous member may be located at a constant distance.

Also, the compressed refrigerant may move to the gas hole providedoutside the porous member through one refrigerant passage.

In order to achieve the objectives of the present invention, there isalso provided a linear compressor including. a linear motor thatcomprises a stator and a mover configured to reciprocate with respect tothe stator; a piston coupled to the mover and configured to move basedon reciprocation of the mover; a cylinder that accommodates the pistonand that defines a compression space together with the piston, thecylinder defining at least one first hole that extends from an innercircumferential surface of the cylinder to an outer circumferentialsurface of the cylinder and that is configured to guide refrigerantdischarged from the compression space to a bearing surface definedbetween the inner circumferential surface of the cylinder and an outersurface of the piston; and a porous member located at the outercircumferential surface of the cylinder and configured to cover the atleast one first hole, the porous member defining micropores having adiameter smaller than a diameter of the at least one first hole.

Here, a cover member that surrounds the porous member and that islocated at an outer circumferential surface of the porous member, thecover member defining at least one second hole that is in communicationwith the micropores of the porous member and that extends from an outercircumferential surface of the cover member to an inner circumferentialsurface of the cover member, a diameter of the at least one second holeis greater than the diameter of the micropores.

Also, a frame that surrounds the cover member and that is located at theouter circumferential surface of the cover member, the frame defining atleast one refrigerant passage configured to guide refrigerant dischargedfrom the compression space to the at least one second hole of the covermember.

Also, a sealing member located at each of a first end of the porousmember and a second end of the porous member.

Also, the cover member surrounds the sealing member and is configured torestrict movement of the sealing member. Also, the cylinder defines anannular recess configured to receive the sealing member and to restrictmovement of the sealing member in the annular recess.

Also, the inner circumferential surface of the cover member is incontact with the outer circumferential surface of the porous member, andthe outer circumferential surface of the cover member is in contact withan inner circumferential surface of the frame. Here, the piston isconfigured to move between a front side of the cylinder and a rear sideof the cylinder opposite to the front side, a volume of the compressionspace being decreasing based on the piston moving from the rear sidetoward the front side, the at least one first hole comprises a pluralityof first holes, the plurality of first holes comprising a plurality offront holes defined at the front side of the cylinder and a plurality ofrear holes defined at the rear side of the cylinder, and the at leastone second hole is located at a position between the plurality of firstholes.

Here, the plurality of front holes are arranged along a lengthwisedirection of the cylinder, the plurality of rear holes are arrangedalong the lengthwise direction of the cylinder, and the at least onesecond hole is located at a position circumferentially between theplurality of front holes and circumferentially between the plurality ofrear holes.

Also, the at least one second hole is located at a position spaced apartby a same distance from each of the plurality of first holes.

In order to achieve the objectives of the present invention, there isalso provided a linear compressor including a casing; a linear motorlocated in an inner space of the casing, the linear motor comprising astator and a mover configured to reciprocate with respect to the stator;a cylinder that is located inside the linear motor and that defines acompression space, the cylinder defining a first hole that extends froman outer circumferential surface of the cylinder to an innercircumferential surface of the cylinder; a piston located inside thecylinder and configured to reciprocate relative to the cylinder based onmovement of the mover, the piston being configured to compressrefrigerant in the compression space; a discharge valve configured toopen and close at least a portion of the compression space; a dischargecover that accommodates the discharge valve, the discharge coverdefining a discharge space configured to receive refrigerant dischargedfrom the compression space; a frame located in the inner space of thecasing and configured to support the cylinder; a porous filter membranethat is located between the outer circumferential surface of thecylinder and an inner circumferential surface of the frame, the porousfilter membrane defining micropores having a diameter smaller than afirst diameter of the first hole; and a shrink tube that surrounds theporous filter membrane and that is located at an outer circumferentialsurface of the porous filter membrane, the shrink tube defining a secondhole having a second diameter larger than the diameter of themicropores, the frame defines a refrigerant passage that allowscommunication between the discharge space and the second hole and thatis configured to guide refrigerant discharged from the compression spaceto the second hole of the shrink tube.

Here, the first hole comprises a plurality of first holes that arearranged along a lengthwise direction of the cylinder, the second holeis located between the plurality of first holes in the lengthwisedirection of the cylinder, and the plurality of first holes are arrangedabout the second hole.

Also, each of the plurality of first holes is located at a positionspaced apart by a same distance from the second hole. A sealing memberlocated at least one of both lengthwise sides of the porous filtermembrane, the shrink tube surrounds the sealing member and is configuredto provide sealing of an end of the porous filter membrane.

Also, the outer circumferential surface of the porous filter membrane isin contact with an inner circumferential surface of the shrink tube, andthe inner circumferential surface of the frame is in contact with anouter circumferential surface of the shrink tube.

In order to achieve the objectives of the present invention, there isalso provided a linear compressor including a casing; a cylinder that islocated inside the casing and that defines a compression spaceconfigured to receive refrigerant, the cylinder defining a cylinder holethat extends from an outer circumferential surface of the cylinder to aninner circumferential surface of the cylinder; a piston located insidethe cylinder and configured to reciprocate relative to the cylinder, thepiston being configured to compress refrigerant received in thecompression space; a porous filter membrane that is located at the outercircumferential surface of the cylinder, the porous filter membranehaving micropores configured to communicate with the cylinder hole; anda refrigerant passage that extends from an outside of the cylinder andthat is configured to guide refrigerant discharged from the compressionspace to an outer surface of the piston through the micropores and thecylinder hole.

A shrink tube that surrounds an outer circumferential surface of theporous filter membrane, the shrink tube defining a tube hole that ispositioned offset from the cylinder hole in a circumferential directionof the cylinder and in a longitudinal direction of the cylinder.

Also, the cylinder hole comprises a plurality of cylinder holes, and thetube hole comprises a plurality of tube holes, and wherein the pluralityof cylinder holes and the plurality of tube holes are alternatelyarranged along a longitudinal direction of the cylinder.

Also, the plurality of cylinder holes comprise: a plurality of firstcylinder holes arranged along a first circumference of the cylinder at afirst longitudinal position of the cylinder; a plurality of secondcylinder holes arranged along a second circumference of the cylinder ata second longitudinal position of the cylinder, the second longitudinalposition being spaced apart from the first longitudinal position in thelongitudinal direction of the cylinder, and the plurality of tube holesare arranged along a tube circumference corresponding to a thirdcircumference of the cylinder between the first longitudinal positionand the second longitudinal position.

Also, each of the plurality of tube holes are configured to receiverefrigerant from the refrigerant passage and supply the receivedrefrigerant to the plurality of cylinder holes through the micropores inthe circumferential direction of the cylinder and in the longitudinaldirection of the cylinder.

Advantageous Effects of the Invention

With the linear compressor according to the present invention,refrigerant can be easily supplied to a bearing surface between acylinder and a piston at an appropriate pressure and in an appropriateamount without a fine nozzle part formed in the cylinder, and thus it ispossible to easily manufacture the cylinder and also to reduce amanufacturing cost for the cylinder accordingly.

Also, with the linear compressor according to the present invention, aporous filter membrane having micropores is inserted into and coupled toan external circumferential surface of a cylinder, instead of arefrigerant passage of a gas bearing being widened and formed in thecylinder, and thus it is possible to appropriately decompressrefrigerant supplied to a bearing surface, thereby reducing the amountof refrigerant leaking into a compression space or an inner space of acasing. Thus, it is possible to increase a substantial load-bearingcapacity for a piston.

Also, not only is the refrigerant passage widened, but also therefrigerant can be filtered through the micropores of the porous filtermembrane to remove foreign substances. Thus, it is possible to preventthe gas bearing from being clogged by the foreign substances.

Also, with the linear compressor according to the present invention, aporous filter membrane is installed on an outer circumferential surfaceof a cylinder, and also a sealing member is installed on both sides ofthe porous filter membrane. Thus, it is possible to restrain refrigerantflowing to the porous filter membrane from leaking into an inner spaceof a casing through both ends of the porous filter membrane instead offlowing to a bearing surface. As a result, it is possible to reduceconsumption of the refrigerant moving from the compression space towardthe bearing surface, thereby decreasing a compression loss and alsoincreasing compression efficiency.

Also, with the linear compressor according to the present invention, gasholes wider than micropores are formed inside and outside a porousfilter membrane, and the inner gas hole is placed at the same distancefrom the outer gas holes. Thus, it is possible to allow the flowdistribution of the refrigerant flowing to the bearing surface to beuniform. As a result, this may allow refrigerant flowing to the bearingsurface to uniformly support the piston in the lengthwise direction,thereby reducing abrasion or friction loss between the cylinder and thepiston.

In addition, it is possible to restrain refrigerant flowing to thebearing surface from flowing into a compression space or from leakinginto an inner space of a casing, thereby reducing a suction loss or acompression loss and thus increasing compression efficiency.

Also, with the linear compressor according to the present invention, gasholes wider than micropores are formed inside and outside a porousfilter membrane, and the outer gas hole are placed in the middlelengthwise with respect to the inner gas hole. Thus, it is possible tosupply refrigerant to both lengthwise sides of the bearing surface.Accordingly, it is possible to restrain the refrigerant from excessivelyflowing into a compression space or an inner space of a casing, therebyreducing consumption of the refrigerant and also uniformly maintaining aload-bearing capacity for the piston.

Also, with the linear compressor according to the present invention, acylinder, a porous filter membrane, a shrink tube, and a frame areplaced as closely as possible. Thus, it is possible to suppress anincrease in outer diameter even though a separate filter member isprovided between the frame and the cylinder and also to increase asealing force for refrigerant.

Also, with the linear compressor according to the present invention,foreign substances can be cut off in the middle of a gas bearing byusing a member with micropores to eliminate filters installed on frontand rear sides of the gas bearing and thus reduce the number ofcomponents. As a result, it is possible to simplify the structure of thecompressor and lower a manufacturing cost thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view showing a linear compressoraccording to the present invention.

FIG. 2 is an enlarged sectional view of a portion of an actuation unitin the linear compressor shown in FIG. 1

FIG. 3 is a perspective view of the linear compressor according to thepresent invention in which a portion of a gas bearing coupled to acylinder is cut out.

FIG. 4 is a sectional view showing the inside of the cylinder containingthe gas bearing in FIG. 3.

FIG. 5 is an enlarged sectional view of part “A” of FIG. 4.

FIGS. 6 and 7 are a sectional view taken along line “V-V” and asectional view taken along line “VI-VI” of FIG. 4. FIG. 6 shows asectional view of the cylinder taken at a location where a second gashole is formed according to this embodiment, and FIG. 7 shows asectional view of the cylinder taken at a location where a first gashole is formed according to this embodiment.

FIG. 8 is a schematic diagram deployed from the front to describe thelocations of the first gas hole and the second gas hole according tothis embodiment, and FIG. 9 is an enlarged schematic diagram of aportion of FIG. 8.

FIGS. 10 and 11 are schematic diagrams of other embodiments ofarrangements of first gas holes and second gas holes according to thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a linear compressor and a refrigerator having the sameaccording to the present invention will be described in detail withreference to embodiments shown in the accompanying drawings.

The linear compressor according to the present invention performs anoperation of suctioning and compressing fluid and discharging thecompressed fluid. The linear compressor according to the presentinvention may be an element of a refrigeration cycle. Hereinafter, afluid will be described below by taking a refrigerant circulating in therefrigeration cycle as an example.

Referring to FIG. 1, a linear compressor 100 according to thisembodiment may include a casing 110 having an inner space 101 forming asealed space and a frame 120 elastically supported by support sprints116 and 117, which will be described below, in the inner space 101 ofthe casing 110. A linear motor 130 (hereinafter used interchangeablywith the actuation unit) may be coupled to and supported by the frame120, and a compression unit 140 for suctioning, compressing, anddischarging refrigerant may be coupled to the linear motor 130. Thus,the compression unit 140 may be coupled to the frame 120 along with thelinear motor 130 and thus may be elastically supported against thecasing 110.

A shell 111 may have an inner diameter variously formed depending on theside of the linear motor 130. However, the linear compressor 100according to this embodiment is not required to be filled with oil inthe inner space 101 of the casing 110 because an oil bearing is excludedand a gas bearing is employed. Accordingly, preferably, the innerdiameter of the shell 111 may be made as small as possible, for example,to a degree that a flange part 122 of the frame 120, which will bedescribed later, will not come into contact with an innercircumferential surface of the casing 110. Thus, an outer diameter ofthe shell 111 of the linear compressor 100 according to this embodimentmay be made much smaller than that in the above-described PatentDocument 1.

The frame 120, which is a portion of a main body C of the compressor, isprovided inside the casing 110. Also, a motor assembly composed of thelinear motor 130 and a cylinder 141 of the compression unit 140 may becoupled to or supported by the frame 120. Thus, the frame 120 may beelastically supported against the casing 110 by a first support spring116 and a second support spring 117, along with the linear motor 130 andthe compression unit 140.

Here, the frame 120 may include a body part 121 formed in a cylindricalshape and a flange part 122 extending radially at a front end of thebody part 121.

An inner stator 132, which will be described later, may be coupled to anouter circumferential surface of the body part 121, and the cylinder 141may be coupled to an inner circumferential surface of the body part 121.However, a porous filter membrane and a shrink tube, which will bedescribed later, are coupled to an outer circumferential surface of thecylinder according to this embodiment, and thus an outer circumferentialsurface of a shrink tub may be in contact with or in close proximity tothe inner circumferential surface of the body. This will be describedbelow again, along with the gas bearing.

An outer stator 131, which will be described later, may be coupled to arear surface of the flange part 122, and a discharge cover assembly 160,which will be described later, may be coupled to a front surface of theflange part 122.

Also, on one side of a front surface of the flange part 122, a bearingentrance recess 125 a forming a portion of the gas bearing, which willbe described later, may be formed, and a bearing communication hole 125b passing from the bearing entrance recess 125 a to the innercircumferential surface of the body part 121 may be formed. A bearingcommunication recess 125 c for enabling the bearing communication hole125 b to communicate with a second gas hole 146 a, which will bedescribed later, may be formed on the inner circumferential surface ofthe body part 121.

The bearing entrance recess 125 a is axially recessed by a predetermineddepth. The bearing communication hole 125 b is a hole with a smallercross-sectional area than that of the bearing entrance recess 125 a andmay be inclined toward the inner circumferential surface of the bodypart 121. Also, the bearing communication recess 125 c may be formed onthe inner circumferential surface of the body part 121 in an annularshape having a predetermined depth and axial length. However, thebearing communication recess 125 c may include an annular recessconnected to the bearing communication hole 125 b and a plurality ofelongated recesses may be connected to the annular recess to extendlengthwise and communicate with a second gas hole, which will bedescribed later.

Meanwhile, the linear motor 130 may include a stator 130 a and a mover130 b reciprocating with respect to the stator 130 a.

The stator 130 a may include an outer stator 131 fastened to the flangepart 122 of the frame 120 and an inner stator 132 spaced a predeterminedgap 130 c from an inner side of the outer stator 131. The inner stator132 may be inserted into and coupled to the outer circumferentialsurface of the body part 121 to surround the body part 121 of the frame120.

The mover 130 b may include a magnet holder 133 a and a magnet 133 bsupported by the magnet holder 133 a. A spring supporter 138 is coupledto a second end of the magnet holder 133 a along with the piston 142,and a first resonance spring 139 a and a second resonance spring 139 bfor resonating the mover 130 b of the linear motor 130 and the piston142 of the compression unit 140 may be provided on both sides of thespring supporter 138.

The compression unit 140 may include the cylinder 141, the piston 142, asuction valve 143, and a discharge valve assembly 144.

The cylinder 141 may be formed in a cylindrical shape to have acompression space 103 b therein may be inserted into or fastened to theinner circumferential surface of the frame 120. A suction mufflerassembly 150, which will be described later, in which refrigerant issuctioned into the compression space 103 b may be provided on a rearside of the cylinder 141, and a discharge cover assembly 160, which willbe described later, in which refrigerant compressed in the compressionspace 103 b is discharged may be provided on a front side of thecylinder 141.

Also, the remaining portion of the gas bearing for supplying dischargedgas to a bearing space or bearing surface 103 c (hereinaftercollectively referred to as a bearing surface) between the cylinder 141and the piston 142 to lubricate a space between the cylinder 141 and thepiston with the gas may be formed in the cylinder 141. For example, afirst gas hole 141 a passing through the outer circumferential surfaceand the inner circumferential surface may be formed in a region of thecylinder 141 for communicating with the bearing communication recess 125c. The first gas hole 141 a serves to guide compressed refrigerantflowing into the bearing communication recess 125 c to the bearingsurface 103 c formed between the inner circumferential surface of thecylinder 141 and the outer circumferential surface of the piston 142.

The first gas hole 141 a may be formed on only a side adjacent to thecompression space 103 b (hereinafter referred to as a front side) withrespect to an axial center of the cylinder and may also be formed on arear side, which is opposite to the front side, in consideration of thedegree of the piston 142 The first gas hole 141 a will be describedbelow again together with the porous filter membrane, the shrink tube,etc. of the gas bearing.

The piston 142 may have a suction flow path 103 a therein and may beformed in a cylindrical shape having an partially open front end and afully open rear end. Also, the rear end, which is an open end asdescribed above, is connected to the magnet holder 133 a so that thepiston 142 may reciprocate together with the magnet holder 133 a.

Also, a suction port 142 a for communication between the suction flowpath 103 a and the compression space 103 b may be formed at the frontend of the piston 142, and a suction valve 143 for selectively openingor closing the suction port 142 a may be provided at the front end ofthe piston 142. Thus, refrigerant suctioned into the inner space 101 ofthe casing 110 may be suctioned into the compression space 103 b in thecylinder 141 through the suction flow path 103 a and the suction port142 a of the piston 142 when the suction valve 143 is opened. Thedischarge valve assembly 144 for opening and closing the compressionspace 103 b may be detachably provided at the front end of the cylinder141, and a discharge cover assembly 160 for attenuating noise generatedwhile refrigerant is being discharged from a discharge space may becoupled onto the front surface of the frame 120. The discharge valveassembly 144 may be accommodated inside the discharge cover assembly160.

The discharge cover assembly 160 may be composed of a single dischargecover or a plurality of discharge cover arranged to sequentiallycommunicate with one another.

For example, when there are three discharge covers, a discharge space(hereinafter referred to a first discharge space) 104 a of a dischargecover (hereinafter referred to as a first cover) 161 coupled to theframe 120 may communicate with a discharge cover (hereinafter referredto as a second discharge space) 104 b of a second discharge cover(hereinafter referred to as a second cover) 162 coupled to a front sideof the first cover 161, and the second discharge space 104 b maycommunicate with a discharge space (hereinafter referred to as a thirddischarge space) 104 c of a third discharge cover (hereinafter referredto as a third cover) 163 coupled to a front side of the second cover162.

Here, the bearing entrance recess 125 a, which has been described above,may be accommodated inside the second discharge space 104 b. Thus,refrigerant flowing into the bearing entrance recess 125 a is notrefrigerant that is discharged from the compression space 103 b anddirectly flows into the first discharge space 104 a, but refrigerantthat moves to the second discharge space 104 b via the first dischargespace 104 a and flows into the second discharge space 104 b. Thus, it ispossible to reduce temperature of refrigerant flowing to the bearingsurface 103 c between the cylinder 141 and the piston 142.

In the drawing, reference numeral 102 denotes a noise space, referencenumerals 112 and 113 denote a rear cap and a front cap, referencenumerals 114 and 115 denote a suction pipe and a discharge pipe,reference numerals 134 and 137 denote a back cover and a stator cover,and reference numerals 144 a and 144 b denote a discharge valve and avalve spring.

The linear compressor according to this embodiment operates as follows.

That is, when electric current is applied to a coil 135 b of the linearmotor 130, a magnetic flux is formed between the outer stator 131 andthe inner stator 132. This magnetic flux causes the mover 130 b composedof the magnet holder 133 a and the magnet 133 b to linearly reciprocatein the gap between the outer stator 131 and the inner stator 132.

Then, the piston 142 connected to the magnet holder 133 a linearlyreciprocates in the cylinder 141, thus increasing or decreasing thevolume of the compression space 103 b. In this case, when the piston 142moves backward to increase d the volume of the compression space 103 b,the suction valve 143 is opened to suction refrigerant of the suctionflow path 103 a into the compression space 103 b. On the other hand,when the piston 142 moves forward to decrease the volume of thecompression space 103 b, the piston 142 compresses refrigerant in thecompression space 103 b. The compressed refrigerant is discharged intothe first discharge space 104 a while opening the discharge valve 144 a.

Then, the refrigerant discharged into the first discharge space 104 amoves to the second discharge space 104 b through the firstcommunication hole 105 a and then moves to the third discharge space 104c through the second communication hole 105 b, a connection pipe 106,and the third communication hole 105 c. In this case, as shown in FIG.2, a portion of the refrigerant moving from the first discharge space104 a to the second discharge space 104 b flows into the bearingentrance recess 125 a forming the entrance of the gas bearing. Thisrefrigerant flows into the bearing communication recess 125 c throughthe bearing communication hole 125 b and then is supplied to the bearingsurface 103 c between the inner circumferential surface of the cylinder141 and the outer circumferential surface of the piston 142 through asecond gas hole 146 a of the shrink tube 146, a micropore 145 a of theporous filter membrane 145, and a first gas hole 141 a of the cylinder141, which will be described later. The high-pressure refrigerantsupplied to the bearing surface 103 c lubricates the space between thecylinder 141 and the piston 142. Then, some of the refrigerant flows outto the compression space, and the other flows out through a suctionspace. The series of courses are repeated.

In this case, when a passage of the gas bearing has a too large innerdiameter, the flow rate of the refrigerant flowing to the bearingsurface 103 c between the cylinder 141 and the piston 142 is excessivelyincreased and thus a large amount of refrigerant flows into thecompression space 103 b or leaks into the inner space 101 of the casing110 . Thus, it is possible to reduce compressor efficiency.

On the other hand, when the passage of the gas bearing has a too smallinner diameter, the passage of the gas bearing is clogged by foreignsubstances or the pressure of the refrigerant flowing between thecylinder 141 and the piston 142 becomes so low that the load-bearingcapacity for the piston 142 is lowered. This causes abrasion or frictionloss between the cylinder 141 and the piston 142, thus reducingcompressor efficiency.

Therefore, in a compressor with a gas bearing, it would be advantageousin terms of compressor efficiency and reliability to supply a properamount of refrigerant to the bearing surface without clogging the gasbearing.

In view of the above description, the gas bearing of the linearcompressor according to the present invention has a member for expandingthe area of the passage of the gas bearing, the member having amicropore in the middle of the passage. Thus it is possible to reducethe consumption flow rate of the refrigerant supplied to the bearingsurface between the cylinder and the piston and also increase thesubstantial load-bearing capacity for the piston.

FIG. 3 is a perspective view of the linear compressor according to thepresent invention in which a portion of a gas bearing coupled to acylinder is cut out, and FIG. 4 is a sectional view showing the insideof the cylinder containing the gas bearing in FIG. 3.

As shown, a plurality of first gas holes 141 a may be formed in thecylinder 141. A porous filter membrane 145 that covers the first gasholes 141 a and has multiple micropores 145 a is inserted into andcoupled to the outer circumferential surface of the cylinder 141. Asecond gas hole 146 a that covers the micropore 145 a of the porousfilter membrane 145 and forms the passage of the gas bearing at apredetermined position may be formed on an outer circumferential surfaceof the porous filter membrane 145.

For example, the plurality of first gas holes 141 a, which have beendescribed above, may be circumferentially formed in the cylinder 141 atregular intervals. The first gas holes 141 a may pass through the outercircumferential surface and the inner circumferential surface of thecylinder 141 and may have the same inner diameter D1. The inner diameterD1 of the first gas holes 141 a may be the same as the inner diameter ofthe bearing communication hole 125 b or may be about 4 mm to 6 mm muchlarger than a general nozzle diameter of 20 μm to 30 μm.

Thus, it is possible to significantly eliminate the possibility that thefirst gas holes 141 a are clogged due to fine foreign substances.However, when the inner diameter of the first gas holes 141 a isenlarged as described above, the refrigerant may excessively flow to thebearing surface. However, this inflow may be suppressed by the porousfilter membrane 145 inserted into the outer circumferential surface ofthe cylinder 141 to cover the first gas holes 141 a.

That is, the porous filter membrane 145 may have multiple micropores 145a formed therein. The micropores 145 a may have a diameter orcross-sectional area significantly smaller than the inner diameter D1 ofthe first gas holes 141 a. The diameter or cross-sectional area of themicropores 145 a may be approximately similar to or greater than aconventional nozzle diameter. When the micropore 145 a has a diametersimilar to or greater than the conventional nozzle diameter, themicropore 145 a may be clogged by foreign substances or may be reducedin pressure drop by half. However, the porous filter membrane 145 itselfis composed of a large number of micropores 145 a. Thus, the micropores145 a, which are passages of the porous filter membrane 145, may not becompletely clogged, and a path through which the refrigerant moves maybe elongated to sufficiently decompress the refrigerant.

Thus, the refrigerant is sufficiently decompressed while passing throughthe porous filter membrane 145 and then flows into the first gas holes141 a. Therefore, it is possible to suppress the pressure of therefrigerant from rising above a necessary pressure even though the innerdiameter D1 of the first gas hole 141 a is large. However, even in thiscase, the traveling distance of refrigerant passing through themicropore 145 a of the porous filter membrane 145 may differ dependingon the locations of the first gas holes 141 a. As a result, the pressureof the refrigerant flowing through in the first gas holes 141 a may beuneven. However, this unevenness may be suppressed by the shrink tube146 that surrounds the outer circumferential surface of the porousfilter membrane 145 and has the second gas hole 146 a provided at apredetermined location. The inner diameter D2 of the second gas hole maybe approximately the same as the inner diameter D1 of the first gashole. However, since the second gas hole 146 a serves as a kind ofrefrigerant passage, the inner diameter of the second gas hole 146 a isnot necessarily the same as the inner diameter of the first gas hole 141a.

That is, the outer circumferential surface of the porous filter membrane145 is surrounded by the shrink tube 146 to restrict the refrigerantfrom flowing to the porous filter membrane 145 in a disorderly fashion.However, by forming the second gas hole 146 a passing from the outercircumferential surface to the inner circumferential surface at anappropriate location of the shrink tube 146, the refrigerant that hasreached the above-described bearing communication recess 125 c may beallowed to flow to the porous filter membrane 145 only through thesecond gas hole 146 a. In this case, the shrink tube 146 is used as acover member. Accordingly, it is preferable that the shrink tube 146 isbrought in close contact with the outer circumferential surface of theporous filter membrane 145 because it is possible not only to increasethe sealing effect on the micropores 145 a but also to prevent the outerdiameter of the compressor from being increased.

In addition, by the shrink tube 146 formed to surround both ends of theporous filter membrane 145, it is possible to suppress a leakage ofrefrigerant from the porous filter membrane 145. In this case, however,the shrink tube 146 may not be able to secure sufficient sealing force.

In view of this, as shown in FIGS. 4 and 5, a sealing member 147 such asan O-ring may be provided at both ends or at least one end of the porousfilter membrane 145. The sealing member 147 may be inserted into asealing recess 141 b provided on the outer circumferential surface ofthe cylinder 141. In this state, the sealing member 147 may be shrunk byboth ends of the shrink tube 146 surrounding the sealing member 147.Thus, the porous filter membrane 145 is completely sealed by the shrinktube 146 and the sealing member, so that the refrigerant flowing intothe second gas hole 146 a can move only to the first gas hole 141 athrough the porous filter membrane 145.

Preferably, the first gas hole and the second gas hole are located asfar from each other as possible because the refrigerant can pass throughthe porous filter membrane for a long time. To this end, it ispreferable that the first gas holes 141 a and the second gas holes 146 aare circumferentially spaced at predetermined intervals from oneanother. FIG. 6 is a sectional view of the cylinder taken at a locationwhere a second gas hole is formed according to this embodiment, and FIG.7 shows a sectional view of the cylinder taken at a location where afirst gas hole is formed according to this embodiment.

As shown in FIGS. 6 and 7, it is preferable that when such first gasholes 141 a are vertically and horizontally formed, the second gas hole146 a is circumferentially formed between the first gas holes 141 a.

Then, when the refrigerant passing through the second gas hole 146 acircumferentially (diagonally in an actual case) moves toward the firstgas holes 141 a, the refrigerant passes through the porous filtermembrane 145. In this case, the distance through which the refrigerantpasses through the porous filter membrane 145 increases, and thus it ispossible to improve the decompressing effect and the filtration effect.

Preferably, the first gas holes 141 a are located at a front side and arear side with respect to the lengthwise direction of the cylinder 141while the second gas hole 146 a is located in the middle between thefront side and the rear side with respect to the lengthwise direction ofthe cylinder 141 such that the second gas hole 146 a is located betweenthe first gas holes 141 a. Here, the front side may be defined as adirection in which the piston 142 moves to decrease the volume of thecompression space 103 b, and the rear side may be defined as theopposite direction.

FIG. 8 is a schematic diagram deployed from the front to describe thelocations of the first gas hole and the second gas hole according tothis embodiment, and FIG. 9 is an enlarged schematic diagram of aportion of FIG. 8.

As shown in the drawings, the first gas holes 141 a are located at frontand rear sides with respect to one second gas hole 146 a, and the secondgas holes 146 a are located in the middle among the first gas holes 141a in the lengthwise direction of the cylinder 141.

Here, the first gas holes 141 a and the second gas hole 146 a may becollinear in the lengthwise direction of the cylinder 141. However, inthis case, the distance between the first gas hole 141 a and the secondgas hole 146 a is narrowed. Accordingly, referring to the positionalrelationship between the first gas hole and the second gas hole shown inFIGS. 6 and 7, this is the same as described in FIG. 8.

That is, first gas holes located at the front side (hereinafter referredto as first front gas holes 141 a 1) and first gas holes located at therear side (hereinafter referred to as first rear gas holes 141 a 2) arecollinear in the lengthwise direction of the cylinder 141. Also, secondgas holes 146 a are located between the first front gas holes 141 a 1and the second rear gas holes 141 a 2. Thus, the number of second gasholes 146 a is smaller than the number of first gas holes 141 a.

In a configuration in which the second gas holes 146 a are occupied incommon, the first front gas holes 141 a 1 and the first rear gas holes141 a 2 are arranged in a zigzag shape

In this case, as shown in FIG. 9, one second gas hole 146 a is locatedin the center of four first gas holes 141 a located in the vicinity, andthe first gas holes 141 a are located at the same distance L1 orapproximately similar distances from the second gas hole 146 a.

Thus, the pressure of the refrigerant flowing into the first gas hole141 a through the second gas hole 146 a may be uniformly maintained,which may be slightly different depending on an arrangement ofmicropores 145 a formed on the porous filter membrane 145.

A process of supplying refrigerant in the discharge space to the bearingsurface between the cylinder and the piston in the linear compressoraccording to this embodiment is as follows.

Referring to FIGS. 3 and 9, the refrigerant discharged from thecompression space flows into the second gas hole 146 a through thebearing entrance recess 125 a, the bearing communication hole 125 b, andthe bearing communication recess 125 c constituting the refrigerantpassage in the second discharge space 104 b. In this case, since thebearing communication recess 125 c is formed in an annular shape on theinner circumferential surface of the frame 120, the refrigerantcircumferentially moves along the bearing communication recess 125 c.

This refrigerant flows into the second gas hole 146 a communicating withthe bearing communication recess 125 c, and the refrigerant flowing intothe second gas hole 146 a flows into the first gas hole 141 a of thecylinder 141 through the micropores 145 a of the porous filter membrane145. Also, the refrigerant flowing into the first gas hole 141 a flowsto the bearing surface between the cylinder 141 and the piston 142 tolubricate the space between the cylinder 141 and the piston 142.

In this case, while passing through the micropores 145 a of the porousfilter membrane 145, the refrigerant passing through the porous filtermembrane 145 is filtered to remove foreign substances and isdecompressed to an appropriate pressure. Accordingly, the pressure ofthe refrigerant flowing to the bearing surface between the cylinder 141and the piston 142 is not excessively higher than the pressure of thecompression space 103 b. Therefore, it is possible to suppress therefrigerant on the bearing surface from flowing into the compressionspace and also to suppress the refrigerant from leaking into the innerspace 101 of the casing, which is a suction space.

Also, the refrigerant passing through the porous filter membrane 145flows in through the second gas hole 146 a and flows out of the firstgas hole 141 a, and thus a path of the micropores 145 a in the porousfilter membrane 145 is elongated. Thus, a sufficient pressure drop maybe generated as the refrigerant stays in the porous filter membrane 145for a long time. Therefore, even though the inner diameter D1 of thefirst gas hole 141 a increases, the flow rate of the refrigerantsupplied to the bearing surface may be appropriately maintained.

Also, the refrigerant flowing into the bearing communication recess 125c of the frame 120 is blocked by the shrink tube 146 not to directlyflow to the porous filter membrane 145 but to flow to the porous filtermembrane 145 through the second gas hole 146 a provided in the shrinktube 146. Also, since distances between the second gas hole 146 a andthe first gas holes 141 a are substantially the same, the pressure ofthe refrigerant flowing to the bearing surface between the cylinder 141and the piston 142 may also be substantially uniform. Thus, Accordingly,the load-bearing capacity of the refrigerant with respect to the piston142 may be uniformly formed because the pressure of the refrigerant isuniformly formed between the cylinder and the piston. This caneffectively suppress abrasion or friction loss between the cylinder 141and the piston 142.

The number of rows of the first gas holes 141 a (for convenience, thelongitudinal direction in the drawing is defined as a row) may be thesame as the number of rows of the second gas holes 146 a. In this case,preferably, the first gas holes 141 a and the second gas hole 146 a maybe spaced at predetermined intervals from one another in the lengthwisedirection or the circumferential direction of the cylinder 141.

For example, when the number of rows of the first gas holes 141 a andthe number of rows of the second gas holes 146 a are all one and thefirst gas holes 141 a and the second gas holes 146 a are radiallycollinear, a path through which the refrigerant moves in the porousfilter membrane 145 may be shortened. Then, the decompression effect ofthe refrigerant may be halved, thus increasing refrigerant consumption.

Accordingly, when the number of rows of the first gas holes 141 a is thesame as the number of rows of the second gas holes 146 a, it ispreferable that the first gas holes 141 a and the second gas holes 146 aare lengthwise and circumferentially spaced at predetermined intervalsfrom one another as shown in FIG. 10 or that the first gas holes 141 aand the second gas holes 146 a are in the same lengthwise direction butare circumferentially spaced at predetermined intervals from one anotheras shown in FIG. 11, in order to elongate the refrigerant travelingpath.

Also, in these cases, it is preferable that the first gas hole 141 acommunicating with the bearing surface be located at the center of thecylinder 141 because the distribution of the refrigerant on the bearingsurface can be made uniform

The arrangement of the first gas holes and the second gas holes may bevariously configured in addition to the embodiments described above.

What is claimed is:
 1. A linear compressor comprising: a linear motorthat comprises a stator and a mover configured to reciprocate withrespect to the stator; a piston coupled to the mover and configured tomove based on reciprocation of the mover; a cylinder that accommodatesthe piston and that defines a compression space together with thepiston, the cylinder defining at least one first hole that extends froman inner circumferential surface of the cylinder to an outercircumferential surface of the cylinder and that is configured to guiderefrigerant discharged from the compression space to a bearing surfacedefined between the inner circumferential surface of the cylinder and anouter surface of the piston; and a porous member located at the outercircumferential surface of the cylinder and configured to cover the atleast one first hole, the porous member defining micropores having adiameter smaller than a diameter of the at least one first hole.
 2. Thelinear compressor of claim 1, further comprising: a cover member thatsurrounds the porous member and that is located at an outercircumferential surface of the porous member, the cover member definingat least one second hole that is in communication with the micropores ofthe porous member and that extends from an outer circumferential surfaceof the cover member to an inner circumferential surface of the covermember, wherein a diameter of the at least one second hole is greaterthan the diameter of the micropores.
 3. The linear compressor of claim2, further comprising: a frame that surrounds the cover member and thatis located at the outer circumferential surface of the cover member, theframe defining at least one refrigerant passage configured to guiderefrigerant discharged from the compression space to the at least onesecond hole of the cover member.
 4. The linear compressor of claim 3,further comprising: a sealing member located at each of a first end ofthe porous member and a second end of the porous member.
 5. The linearcompressor of claim 4, wherein the cover member surrounds the sealingmember and is configured to restrict movement of the sealing member. 6.The linear compressor of claim 5, wherein the cylinder defines anannular recess configured to receive the sealing member and to restrictmovement of the sealing member in the annular recess.
 7. The linearcompressor of claim 3, wherein the inner circumferential surface of thecover member is in contact with the outer circumferential surface of theporous member, and wherein the outer circumferential surface of thecover member is in contact with an inner circumferential surface of theframe.
 8. The linear compressor of claim 2, wherein the piston isconfigured to move between a front side of the cylinder and a rear sideof the cylinder opposite to the front side, a volume of the compressionspace being decreasing based on the piston moving from the rear sidetoward the front side, wherein the at least one first hole comprises aplurality of first holes, the plurality of first holes comprising aplurality of front holes defined at the front side of the cylinder and aplurality of rear holes defined at the rear side of the cylinder, andwherein the at least one second hole is located at a position betweenthe plurality of first holes.
 9. The linear compressor of claim 8,wherein: the plurality of front holes are arranged along a lengthwisedirection of the cylinder, the plurality of rear holes are arrangedalong the lengthwise direction of the cylinder, and the at least onesecond hole is located at a position circumferentially between theplurality of front holes and circumferentially between the plurality ofrear holes.
 10. The linear compressor of claim 9, wherein the at leastone second hole is located at a position spaced apart by a same distancefrom each of the plurality of first holes.
 11. A linear compressorcomprising: a casing; a linear motor located in an inner space of thecasing, the linear motor comprising a stator and a mover configured toreciprocate with respect to the stator; a cylinder that is locatedinside the linear motor and that defines a compression space, thecylinder defining a first hole that extends from an outercircumferential surface of the cylinder to an inner circumferentialsurface of the cylinder; a piston located inside the cylinder andconfigured to reciprocate relative to the cylinder based on movement ofthe mover, the piston being configured to compress refrigerant in thecompression space; a discharge valve configured to open and close atleast a portion of the compression space; a discharge cover thataccommodates the discharge valve, the discharge cover defining adischarge space configured to receive refrigerant discharged from thecompression space; a frame located in the inner space of the casing andconfigured to support the cylinder; a porous filter membrane that islocated between the outer circumferential surface of the cylinder and aninner circumferential surface of the frame, the porous filter membranedefining micropores having a diameter smaller than a first diameter ofthe first hole; and a shrink tube that surrounds the porous filtermembrane and that is located at an outer circumferential surface of theporous filter membrane, the shrink tube defining a second hole having asecond diameter larger than the diameter of the micropores, wherein theframe defines a refrigerant passage that allows communication betweenthe discharge space and the second hole and that is configured to guiderefrigerant discharged from the compression space to the second hole ofthe shrink tube.
 12. The linear compressor of claim 11, wherein thefirst hole comprises a plurality of first holes that are arranged alonga lengthwise direction of the cylinder, wherein the second hole islocated between the plurality of first holes in the lengthwise directionof the cylinder, and wherein the plurality of first holes are arrangedabout the second hole.
 13. The linear compressor of claim 12, whereineach of the plurality of first holes is located at a position spacedapart by a same distance from the second hole.
 14. The linear compressorof claim 11, further comprising: a sealing member located at least oneof both lengthwise sides of the porous filter membrane, wherein theshrink tube surrounds the sealing member and is configured to providesealing of an end of the porous filter membrane.
 15. The linearcompressor of claim 14, wherein the outer circumferential surface of theporous filter membrane is in contact with an inner circumferentialsurface of the shrink tube, and wherein the inner circumferentialsurface of the frame is in contact with an outer circumferential surfaceof the shrink tube.
 16. A linear compressor comprising: a casing; acylinder that is located inside the casing and that defines acompression space configured to receive refrigerant, the cylinderdefining a cylinder hole that extends from an outer circumferentialsurface of the cylinder to an inner circumferential surface of thecylinder; a piston located inside the cylinder and configured toreciprocate relative to the cylinder, the piston being configured tocompress refrigerant received in the compression space; a porous filtermembrane that is located at the outer circumferential surface of thecylinder, the porous filter membrane having micropores configured tocommunicate with the cylinder hole; and a refrigerant passage thatextends from an outside of the cylinder and that is configured to guiderefrigerant discharged from the compression space to an outer surface ofthe piston through the micropores and the cylinder hole.
 17. The linearcompressor claim 16, further comprising: a shrink tube that surrounds anouter circumferential surface of the porous filter membrane, the shrinktube defining a tube hole that is positioned offset from the cylinderhole in a circumferential direction of the cylinder and in alongitudinal direction of the cylinder.
 18. The linear compressor ofclaim 17, wherein the cylinder hole comprises a plurality of cylinderholes, and the tube hole comprises a plurality of tube holes, andwherein the plurality of cylinder holes and the plurality of tube holesare alternately arranged along a longitudinal direction of the cylinder.19. The linear compressor of claim 18, wherein the plurality of cylinderholes comprise: a plurality of first cylinder holes arranged along afirst circumference of the cylinder at a first longitudinal position ofthe cylinder; a plurality of second cylinder holes arranged along asecond circumference of the cylinder at a second longitudinal positionof the cylinder, the second longitudinal position being spaced apartfrom the first longitudinal position in the longitudinal direction ofthe cylinder, and wherein the plurality of tube holes are arranged alonga tube circumference corresponding to a third circumference of thecylinder between the first longitudinal position and the secondlongitudinal position.
 20. The linear compressor of claim 18, whereineach of the plurality of tube holes are configured to receiverefrigerant from the refrigerant passage and supply the receivedrefrigerant to the plurality of cylinder holes through the micropores inthe circumferential direction of the cylinder and in the longitudinaldirection of the cylinder.